1. Field of the Invention
The present invention relates to a method for effectively removing a thermal sleeve from a reactor coolant system when the thermal sleeve is unintentionally separated from the system.
2. Description of the Related Art
In general, a reactor coolant system incorporates a safety injection pipe to supply safety injection water, in order to assure cooling of a reactor core in the event of an emergency situation. The safety injection pipe is provided with a thermal sleeve at a junction of the safety injection pipe and a reactor coolant pipe to minimize the effect of thermal shock of a hot reactor coolant and cold safety injection water on the pipes.
The thermal sleeve, installed as described above, may undergo unintentional separation or position displacement due to fluid streams, external vibration, or the like in the course of operation. Once the thermal sleeve is unintentionally separated, it is necessary to effectively remove the separated thermal sleeve so as not to have a negative effect on the operation of a power plant.
However, since the thermal sleeve is located in a highly radioactive region close to a nuclear reactor and is filled with a boric acid solution for radiation shielding, it is actually impossible for a person to access the thermal sleeve.
Therefore, in a conventional method for removing a thermal sleeve, a safety injection pipe is first cut and thereafter, a thermal sleeve is removed by use of cutting equipment. However, implementation of such a cutting operation may disadvantageously increase a removal operation period and also, may entail problems including reliability deterioration due to cutting and repetitious welding of a major system, enormous removal costs, invasion of impurities, and the like.